persistent-template without persistent

[mikelpr]

I had been using persistFileWith the same model I used for my backend on my miso app perfectly, until I updated to newer miso and ghcjs and my nix pins in general.

Unfortunately, network-2.8 doesn't build with ghcjs so it fails. after many hours debugging, I found out the culprit was monad-loggers due to conduit-extra.

I don't actually need persistent for the frontend I only need its template parsing to produce the data definitions

[parsonsmatt]

This should be relatively straightforward, but it would require work to factor out a persistent-core package that only defines the relevant data types and class instances.